NBC News’s Chuck Todd teed up Sen. Elizabeth Warren (D-Mass.) nicely during the first part of last week’s first Democratic debate.

You have plans for everything, Todd said. Do you have a plan for dealing with Senate Majority Leader Mitch McConnell (R-Ky.) if you win the presidency but Republicans hold the Senate in 2020 — and McConnell reverts to his Obama-era efforts to blockade Democratic priorities?

"I do,” Warren said with confidence, earning boisterous applause.

If she does, she didn't share it with Todd. Instead, she told him that her plan was to ensure that voters energized by the presidential race stayed energized.

"We have to push from the outside, have leadership from the inside, and make this Congress reflect the will of the people,” she said.

In other words, Warren argues that McConnell will be swayed by active, vocal Warren supporters — an argument that seems at odds with everything we know about him.

Other Democrats were asked the same question: How would they deal with a Republican-controlled Senate if they want to get anything done? Former congressman John Delaney (D-Md.) offered a slightly less nuanced version of Warren’s argument: We’ll just work together on “ideas that work.” Sen. Cory Booker (D-N.J.) responded by giving an example of an idea that worked: criminal justice reform, which President Trump signed into law. Granted, he admitted, the bill that was enacted was “not as far as I wanted to go.” It was also a bill that Trump supported — meaning that McConnell did, too. If Booker were president, McConnell would probably not be as accommodating of the White House.

The problem for those Democrats is that there isn't an easy answer.

The Senate, like the electoral college in 2016, is weighted in a way that benefits Republicans. Trump won 30 states in 2016 on the strength of losing the popular vote by nearly 3 million ballots. That’s the equivalent of winning 60 percent of the seats in the Senate despite winning 46 percent of the vote. Trump is president because he won a still-disproportionate 57 percent of the electoral votes that were up for grabs.

Trump's win three years ago spurred a great deal of hand-wringing about how Democrats failed. One prominent line of argument centered on a need for the party to perform better with white working-class voters, particularly in Rust Belt states that Trump unexpectedly secured. That Hillary Clinton didn't travel to Wisconsin during the waning days of the campaign has become an in-joke about the failures of her campaign, not that it's exactly wrong. But for 78,000 votes in Michigan, Pennsylvania and Wisconsin, Clinton is president. Win 78,000 more working-class white voters in these states where manufacturing evaporated, and Trump's job is once again hosting “Celebrity Apprentice.”

There’s another way to look at what happened in 2016, though, one that many of the candidates seeking the 2020 Democratic nomination seem to have internalized.

About 4.4 million people who supported Barack Obama in 2012 didn’t come out to vote in 2016, according to analysis published last year. About half of those nonvoters were nonwhite. Other analysis, including from Pew Research Center, bolsters those numbers. About three-quarters of those in Pew’s pool of 2016 voters were white, but whites only made up only half of the pool of nonvoters.

The idea is this: Boost nonwhite turnout in 2016, and you could similarly have eaten into or erased that 78,000-vote margin. White working-class voters have been trending more and more Republican over time, according to Gallup. (Their support for Trump was seemingly not really a function of Trump himself, though their turnout might have been.) Winning over those voters seems like a bigger task than turning out people who had voted previously.

There’s been a push among some Democratic Party activists to support a nonwhite nominee in next year’s contest in hopes that voters sidelined in 2016 might come to the polls. A Pew poll from May shows that Democrats express more enthusiasm about voting for a black or Hispanic nominee in 2020 than a white one, particularly a white male.

This is a tension in the race. Should Democrats focus on white working-class voters in Rust Belt states in an effort to replay the 2016 election? Or should they instead focus on embracing the party’s diversity and issues important to nonwhite voters in hopes that more people will be interested in coming out to vote?

Rep. Tim Ryan (D-Ohio) argued for the former in last Wednesday's debate.

"We have a perception problem with the Democratic Party,” he said. “We are not connecting to the working-class people in the very states that I represent, in Ohio, in the industrial Midwest. We’ve lost all connection. We have got to change the center of gravity of the Democratic Party from being coastal and elitist and Ivy League, which is the perception, to somebody from the forgotten communities that have been left behind for the last 30 years, to get those workers back on our side.”

This obviously serves Ryan well, given that he represents a working-class district near the near-mythical city of Youngstown. But he also made an important ancillary point: Such a shift would be required to overcome McConnell's opposition by ousting Republicans from key Senate seats.

"If you want to beat Mitch McConnell,” he continued, “this better be a working-class party. If you want to go into Kentucky and take his rear end out, and if you want to take [Sen.] Lindsey Graham out, you’ve got to have a blue-collar party that can go into the textile communities in South Carolina.”

This is the tension in the party. Can Democrats be a diverse party that’s rooted in coastal cities and still win races in South Dakota or Kansas? They don’t need to win Kansas to win the presidency. Heck, they don’t need to win Wisconsin, Michigan or Pennsylvania either: Just camp out in Texas and put all your chips on flipping that state to blue, and even Clinton gets an electoral college win. But Democrats might want to pick up a Senate seat in Kansas to take a majority in that chamber.

The states where the Democrats have the best chance of picking up seats next year, according to Cook Political Report, are Arizona, Colorado and Maine. Only Arizona went for Trump, and fairly narrowly. But they need at least four gains to get 50 votes, including holding a seat in Alabama. The next states within reach for the party are Georgia, Iowa, Kentucky, Mississippi, North Carolina, Tennessee and, yes, Kansas. On average, Trump won those states by 16 points. The closest was North Carolina, which he won by four. This isn’t unachievable, but it’s an uphill climb.

Republicans, though, don’t seem to have a similar problem. Their party is more homogeneous demographically and — particularly in the era of Trump — rhetorically. Democrats are known for their ferocious infighting, but that’s in part because the party includes a broader range of constituencies jockeying for attention. The GOP has been very effective at highlighting those conflicts in ways that, fairly or not, portray Democrats as out of touch with their own base.

It’s largely true that Republican nominee in 2020 (that is, Trump) can make his pitch to Republicans across the board without having to worry about alienating sympathetic voters in Senate races. Given the prominence of the 2020 presidential race and its saturation of media coverage, the national message could, however, put Democratic Senate candidates in red states in a tough position. Do they mirror the national party rhetoric or do they try to fight the tide?

After the 2018 midterms, two losing red-state Democrats blamed that national tide directly. Indiana’s Joe Donnelly lamented the party’s discussions of Medicare-for-all shortly after his loss. Claire McCaskill of Missouri echoed Ryan: “Will we ever get to a majority in the Senate again, much less to 60, if we do not have some moderates in our party?”

Many Democrats would respond curtly: Sure. Medicare-for-all polls fairly well, at least in the abstract; perhaps the problem was Donnelly as much as the environment. During last week’s debate, New York Mayor Bill de Blasio offered that sort of argument for defeating McConnell.

"If the Democratic Party would stop acting like the party of the elites and be the party of working people again, and go into states, including red states, to convince people we’re on their side,” he said, “we can put pressure on their senators to actually have to vote for the nominees that are put forward.”

We may be presenting a false choice. Is there a Democratic Party that is reflective of its diverse base and that also unifies around an economic message that appeals to whites in red states? But if so, will the party’s 2020 nominee try to square that circle at the possible expense of turning out presidential voters?

Or is the party, like the Republicans, simply in a demographic eddy, waiting out demographic shifts (increasing nonwhite population, aging boomers) that will tip national politics to its advantage? The 2020 election may not satisfactorily answer that question.